The present invention relates to a stair-climbing vehicle, in particular to a stair-climbing vehicle for transporting a wheelchair with a person sitting on.
In fact, the applicant of this application has suggested a stair-climbing vehicle for wheelchair, which was disclosed in Japanese Patent Application Laid-open No. 4-154493, as illustrated in FIG. 7. Referring to FIG. 7, the conventional stair-climbing vehicle comprises a crawler device a which includes a pair of endless belt crawlers each extending in the longitudinal direction thereof over at least two steps of a stairway while climbing up or down the stairway, a load-carrying platform C for holding a wheelchair with a person sitting on, two pairs of travelling wheels C1 (with one pair provided under the front portion of the load-carrying platform C and another pair provided under the rear portion thereof), an electric cylinder b for pivotally raising the load-carrying platform C, an operation handle d for operating the stair-climbing vehicle.
When travelling on a horizontal ground surface, the electric cylinder b is caused to retract so that all the travelling wheels C1 will get in contact with ground surface. When climbing up or down a stairway, a change-over switch (not shown) provided on the operation handle d is operated to cause the cylinder b to extend, so that the load-carrying platform C is pivotally raised up to form an angle of 40.degree. with respect with the crawler device a.
In this way, as shown in FIG. 7, a person sitting on the wheelchair may be moved up or down a stairway with his wheelchair slightly inclined rearwardly. In practice, in order to eliminate an uncomfortable or even a terrible feeling, the load-carrying platform C is designed to be able to incline rearwardly a little when travelling up or down a stairway, such that the load-carrying platform C forms an angle of 5.degree.-10.degree. with a horizontal plane.
However, when the stair-climbing vehicle is climbing up or down a stairway which has only a small inclining angle with a horizontal plane, the loading stand C will be inclined rearwardly too much if load-carrying platform C remains an angle of 40.degree. with respect with the crawler device a. As a result, because the load-carrying platform is rearwardly inclined too much, a person sitting on the wheelchair will have an uncomfortable or even a terrible feeling. In order to solve such a problem, it has been suggested that an inclination sensing/controlling device be provided to detect such an angle. But, if an inclination sensing/controlling device is employed, it will be unavoidable to cause an increase in the cost for the manufacture of a stair-climbing vehicle.